Fc receptor block is never (in my opinion) a must during flow cytometry. What it does is mainly reduce "false positive" events, so adding it to your protocol will generate "cleaner" results. Even so - flow cytometry without Fc receptor block should not be a problem, especially when looking into large populations such as T cells.

Another note - as I see it, the "false positive" is being reduced statistically "even" from all the existing populations in the sample, hence - the results will be cleaner, but pretty much similar. 

I'm pretty sure that T cells don't express Fc receptors, so as long as you're gating on a T cell specific marker like CD3/4/8 you should be ok :)

I depends! It should not be necessary if you're looking at a sorted T-cell population or T-cell line (although actually I'd still do it if the cells were sorted). However whatever you're doing tissues (spleen, LN, ...) I would definitely say yes! You'll avoid unspecific staining and will be more sure about results!

If you are looking at tissue, you may want to, if you are looking at spleen it may not be necessary.  I use Fc block when staining myeloid populations and when looking at T cell populations isolated from intestinal tissue but I don't think it makes a difference when looking at spleen.

To stain T-cells, blocking Fc receptors is not essential.

However, if you care about cost and are looking at T-cells among tissue cells, you may want to use it because it will greatly increase the specificity of your staining -->all of your antibodies are staining the surface molecules you want and are not binding to Fc receptors on macrophages and dendritic cells. So you can use less antibody per sample (more cost effective).

If you are considering sorting and RNAseq, I would recommend Fc blocking as you will also minimize contamination of your population of interest.